Many food products containing and including edible fats and oils, i.e., fats and oils of animal and vegetable origin or modified fats and oils of animal and vegetable origin, become rancid or have an undesirable taste and/or color imparted thereto during storage, especially upon exposure to or on contact with oxygen. A number of chemical compounds have been employed for avoiding or reducing these effects so that food products containing fats or oils may be kept for longer periods of time, but such agents have not been entirely satisfactory or effective in many cases. Furthermore, such chemical compounds are usually synthetic chemical products not derived from or identical with material of natural food classifications and, as a consequence, there has been some question as to the advisability of using such compounds in food compositions.
Principal antioxidants of the above kinds heretofore employed included BHA (butylated hydroxyanisole), BHT (butylated hydroxytoluene) and TBHQ (tertiary butylhydroquinone), as well as some other chemicals of which one example is propyl gallate (PG). While these materials have been quite effective in animal fats, such as lard, they are much less useful in some other applications. Their volatility and tendency to decompose at high temperatures makes them not entirely suitable for deep fat fried foods. Indeed, their usefulness for the stability of vegetable oils is less than satisfactory. For example, they are not entirely effective in protecting against off-flavor development, such as the so-called reversion flavor, that occurs, with passage of time, in soybean oil. For these and other reasons, there has been a need for improvement in the field of antioxidants, especially those to be used with food materials that comprise or consist of fats or oils.
It has heretofore been found that antioxidant properties are possessed by tempeh, a fermented soybean product, obtained by fermenting soybeans with a fungus, either Rhizopus oligosporus or Rhizopus oryzae, and food products containing tempeh, such as fish or fatty meat food products, exhibit improved stability, see U.S. Pat. No. 3,681,085 (1972). It has further been heretofore found that by extracting tempeh with a mixture of hexane and ethanol, a component of tempeh, namely oil of tempeh, can be recovered, see U.S. Pat. Nos. 3,762,933 (1973) and 3,855,256 (1974). Oil of tempeh demonstrates improved antioxidant properties over those of unextracted tempeh. Although the aroma of tempeh and oil of tempeh is an essentially mild and pleasant one, the use of these materials is limited to situations where their basic flavors are desired or at least tolerable.
Although the chemical additives described above are essentially tasteless and odorless, their non-natural or synthetic origin creates problems. There is a need in the food industry for an antioxidant derived from natural foodstuffs and which has superior properties and can serve a wide range of uses.